Washing of blood cells is required e.g. when frozen and glycerolized red blood cells are to be reconstituted for transfusion to a recipient. After thawing, the blood cells are liberated from glycerol and other undesired components by repeated washing steps using a wash solution. Blood cells which have been processed by techniques other than glycerolization and freezing so as to be capable of long-term storage likewise have to be washed free of additives before they can be transfused to a recipient.
U.S. Pat. No. 3,326,458, U.S. Pat. No. 3,679,128, U.S. Pat. No. 3,737,096 and U.S. Pat. No. 3,858,796 disclose examples of methods for batch washing of blood cells and of centrifuges and container assemblies for use in carrying out such washing methods.
More particularly, U.S. Pat. No. 3,326,458 discloses batch washing of glycerolized red blood cells in a system of closed collapsible containers of flexible material which are positioned concentrically in a centrifuge rotor. An annular processing or primary container holds the cells to be washed and communicates through collapsible conduits with other containers, including a circular, centrally positioned wash liquid container and an annular waste container which is positioned radially outwardly of the primary container. Pinch valves are provided to control the flow between the primary container, on the one hand, and the wash liquid container and the waste container, on the other hand.
When a batch of thawed glycerolized red blood cells held in the primary container is to be reconstituted, the centrifuge rotor is spun at appropriate speed until the red blood cells have sedimented in the radially outer portion of the primary container. While the rotor is spinning, the valve controlling the flow from the primary container into the waste container is opened to allow the glycerol supernatant to flow into the waste container. To this end, a predetermined volume of compressing liquid is centrifugally actuated to cause compression of the primary container so that an equal volume of supernatant is expressed from it.
Following closing of the just-mentioned valve, the valve controlling the flow from the wash liquid container into the primary container is opened to allow wash liquid to flow under action of the centrifugal field into the primary container, thereby expanding it and displacing the compressing liquid against action of the centrifugal field. The wash liquid mixes with the pack or concentrate of red blood cells and is then centrifugally separated from the cells to form a supernatant which is subsequently expressed into the waste container in the manner described above with reference to the glycerol supernatant.
The steps of admitting a predetermined volume of wash liquid into the primary container and subsequently expressing it into the waste container together with liberated contaminating substances are repeated until the red blood cells are clinically acceptable.